PHP: Regex to camelCase a dashed/underscored string & test against native functions

Solution:

public function getMethod($action) {
    // Patterns to match underscores, dashes, or spaces followed by a character
    $pattern = array('/_(.?)/e', '/-(.?)/e', '/ (.?)/e');

    // Replace matched character with its uppercase version to convert to camelCase
    $action = preg_replace($pattern, 'strtoupper("$1")', $action);

    // Check if function exists or is a reserved method name
    if (function_exists($action) || in_array($action, ['list', 'new', 'sort'])) {
        return '_'.$action; // Prefix with underscore if it’s a reserved name
    } elseif ($action == '') {
        return 'index'; // Default method if empty
    } else {
        return $action;
    }
}

Notes & Modern PHP Update

Deprecated /e modifier:

The /e modifier in preg_replace is deprecated in PHP 5.5+ and removed in PHP 7.

Use preg_replace_callback instead for safer modern code.

Modern version using preg_replace_callback:

public function getMethod($action) {
    $action = preg_replace_callback('/[_\-\s](.?)/', function($matches) {
        return strtoupper($matches[1]);
    }, $action);

    if (function_exists($action) || in_array($action, ['list', 'new', 'sort'])) {
        return '_'.$action;
    } elseif ($action == '') {
        return 'index';
    } else {
        return $action;
    }
}

This approach safely converts my_function-name or my function name → myFunctionName.

Works in PHP 7+ without deprecated warnings.